As defined by IEEE 802.1ag (Ethernet Connectivity Fault Management), Maintenance Association End Points (MEP's) are created on various switch elements across a network to create a Maintenance Association (MA). Periodically each MEP sends a Connectivity Fault Management (CFM) packet as a multicast Continuity Check Message (CCM) to inform other MEP's in the MA that the link between the two is still operational. The interval of the CCM transmission typically should be about the same for all MEP's in the MA. The intervals allowed by the standard are 3.3 ms, 10 ms, 100 ms, 1-s, 10-s, 1-m and 10-m. This design is implemented under the assumption that increasing the interval will allow a local MEP to handle more peers as the reception of CCM's will be at the same or lower rate if the number of peers is increased and the interval increased. For example, if the MA expands from 100 MEP's to 1000 MEP's, but the load on the network and the load on the CCM reception is required to stay the same, the operator could increase the CCM interval from 1-s to 10-s.
Increasing the interval, however, can be problematic. There is no system design in place to prevent these 1000 MEP's from transmitting all their CCM's at the same time. As a result, a MEP could receive a burst of 1000 CCM's. It is unlikely that its queue will be able to hold all the CCM's. This leads to the majority of them being dropped. In an alternative approach to solve this problem, the CCM interval could be increased to one minute, but the same burst problem could exist. Also, there are a number of factors that increase the likelihood of MEP's in a MA dropping the packets. For example, as the CFM service is initially provisioned across the network, it is enabled at the same time on all devices to prevent false alarms during the MA configuration. Another factor is when a MEP detects a fault in an MA, it expedites a CCM and restarts its transmission timer. Certain faults in a MA will be detected by all MEP's at the same time, leading them to expedite a CCM and restart their transmission timers in synchronization.